Typewriter and like separably interfitted stem and molded cap keys



March 13, 1951 c. H. BRADT 2,545,133

TYPEWRITER AND LIKE SEPARABLY INTERFITTED STEM AND MOLDED CAP xsys Filed April 15, 1949 FIG. 2

FIG.

FIG.4

CHARLES H. BRADT INVENTOR ATTORNEY Patentecl Mar. 13, 1951 TYPEWRITER AND LIKE SEPARABLY INTER- rrr'rno STEM AND MOLDED CAP KEYS Charles H. Bradt, Groton, N. Y., assignor to L. C.

Smith & Corona Typewriters, Inc., Syracuse, N. Y., a corporation of New York Application April 15, 1949, Serial No. 87,814

12 Claims.

-Keys of the kind comprising a metal key stem and a molded key cap or button which is detach ably fitted on and about one end of the stem have been employed extensively for many years in typewriters, computing machines and other key operated and key controlled machines and devices notwithstanding long known disadvantages inherent in keys of this kind as heretofore constructed.

The molded cap or button elements of such keys have been formed of various moldable plastic compositions, the compositions most commonly used being thermosetting and thermoplastic synthetic resin plastics.

The molded caps of such known keys have objectionable tendencies to fracture during application of the cap to the stem and under repeated finger impacts on the key in use thereof, to b come loose on the stem and accidentally disconnected from the stem, to become tilted relatively to the stem when forced on the stem or under finger impacts in use of the key, and to partially rotate or oscillate relatively to the stem. Such caps have been slipped directly upon metal rods or sheet metal bars of small transverse section and forming the stem of the key.

Efforts heretofore made to avoid the above recited disadvantages of such keys have been only partially successful and have resulted in key caps or buttons of excessive and unsightly thickness, the caps of such keys usually being at least about one-third of an inch thick and being objectionable from the standpoints of appearance and of the amount of material required to form the cap. In some cases the appearance of the key has been enhanced and the amount of material required has been reduced, at the expense of reduced strength of the key cap, by formin the 7 cap below its finger contact face with a reduced or laterally constricted and consequently weakened portion having a stem receiving socket therein. The reduced stem receiving portions of such key caps have in some cases been provided, at substantially increased cost, with metal reinforcement around the stem receiving socket.

The caps of such keys are commonly provided with a character, numeral or other indicia visible at the obverse face of the key, and one extensively employed method of forming such caps is by the well-known two-shot injection molding process by which the character part of the cap is formed of plastic of one color and the remaining part of the cap is formed of plastic of a contrasting color, said parts being formed one after the other and both extending from face to face of the key cap. Injection molded, two-color key caps of this type cannot conveniently be formed unless the characters are of less face size than that of the bottom face of the key cap, so that reduction of cross section of the lower part of a key cap so molded requires an objectional reduction in the face size of the character.

The present invention provides an improved key of the general kind set forth above which is free from the aforesaid disadvantages and objections, and also provides improved detachably and directly endwisely interfittable metal stem and molded cap or button elements of such keys.

Particularly the invention provides stem and button key elements which are respectively interfittable by relative endwise thrust toward each other while in a particular relatively rotated position, are pullable apart when desired, will maintain tight holding frictional engagement against accidental pulling apart notwithstanding the fact that the cap is molded of a material which is subject to contraction and/or expansion due to age, changes of atmospheric temperature and/or humidity, or other reasons, and are shaped to so mutually separably engage that accidental relative tilting and rotating movements therebetween are prevented and that the cap may be made quite thin (of the order for example of /32 of an inch) but nevertheless will have a large total surface area in tight holding frictional engagement with the stem and be so supported by the stem that liability of fracture of the cap during actuation of the key is substantially entirely obviated.

The invention also provides a key of the class set forth wherein the key stem has a flat head portion to which the main body portion of the stem is normal and which is provided with an off center aperture therein, and wherein the molded cap is socketed to receive and seat on said head portion of the stem and to frictionally engage said head portion about the outer edge of said portion and about the edge of said off center aperture.

In the accompanying drawing:

Figure 1 is a top plan view of a typewriter key embodying the invention in its preferred form;

Figure 2 is a vertical sectional view on the line 2-2 of Figure l;

Figure 3 is a top plan View of the metal stem of the key;

Figure 4 is a bottom plan View of the molded plastic cap or button of the key; and

Figures 5 and 6 are views similar to Figure 3 showing the stem parts of two modified forms of typewriter keys embodying the invention.

Referring particularly to the drawing, the key shown in Figures 1 to 4 has a metal stem Ill-4i and a molded cap or button l2 formed of synthetic resin. The key stem shown is a unitary sheet metal stamping, formed from stock preferably having a thickness of about /64 of an inch, and has a straight and fiat bar-like main body portion and a fiat head portion II which are integrally joined at one end of the main body portion of the stem and are arranged with said stem portion normal to said flat head portion and with the head portion covering the adjacent end of the stem portion of the key and protruding laterally therefrom. The key shown has the other end of its stem integrally joined with one end of a sheet metal typewriter key lever l3, only a fragment of which is shown, but it will be obvious that the key stem may be movably supported and guided in other known ways, as is common in typewriting and other key controlled and key operated machines. The obverse or finger-contact face of the key cap preferably is dished or concave, as shown in Figures 1 and 2, and as is common in the art.

The :plastic key cap i2 is molded with a recess is in the reverse face of the cap, which recess is so shaped as to provide the cap within the recess with a holding projection I5 which is located off center or eccentrically with respectto the center of the key cap, and also to provide the cap at said face with a tubular holding projection or skirt portion 16 exteriorly bounding said recess. The head portion H of the metal key stem is provided with an aperture i! which is located off center or eccentrically with respect to the center of said head portion. The projection I5 and aperture ii are of corresponding size and shape in plan for tight fitting of the projection in the aperture with the projection engaged with the edge of the aperture at least substantially entirely therearound.

The bottom of recess i4 is flat and normal to the vertical axis of the disk-like cap. The recess is of such depth as to completely receive the head portion H of the stem and, while the depth of such recess may be several times greater than the thickness of said head portion, if desired, there is no need for it to be of such relatively great depth and preferably, as shown, its depth only very slightly exceeds the thickness of said head portion of the stem. The internal periphery of the tubular holding projection or skirt portion l6 of the cap and the external periphery of the apertured head portion of the stem are of identical size and shape substantially entirely therearound for tight fitting frictional engagement of the skirt portion about said head portion substantially entirely around the outer edge of the head portion.

The key is assembled by forcibly pushing the cap onto the head portion of the stem until it seats fiatly on said head portion, and the key may be disassembled by forcibly pulling the cap off the stem. The projection l5 must be registered with aperture i1 before the key can be assembled.

While the key is in assembled condition, the cap and stem are positively interlocked against relative rotation with the cap in a predetermined relatively rotated position with respect to the stem. Any indicia provided in a predetermined position on the cap obviously may be fixedly located with respect to the key stem simply by coupling the stem and cap portions of the key. The extremely small necessary penetration of the key stem into the key cap, and the fact that the head portion of the key stem firmly backs up and seats the cap not only at and adjacent the center of the cap but also adjacent the periphery of the cap, makes possible the use of a thin cap while providing a sturdy key in which both fracturing of the cap and tilting of the cap relatively to the stem under finger impacts are at least substantially entirely obviated and great endwise pulling force must be intentionally exerted to disconnect the cap and stem. While the cap frictionally grips only the internal and external perimetrical edge faces of the apertured and thin sheet metal head portion of the stem, these very narrow faces extend around the aperture l1 and the exterior edge of the head and their total area consequently is so large and so advantageously distributed for contact with the cap that an extremely strong friction grip between the cap and the stem is afforded. Moreover, when the grip between the cap and the head of the stem around one of said two perimetrical edges of the apertured head of the stem tends to relax due to expansion or shrinkage of the plastic cap, the grip around the other one of said head edges will increase.

The molded cap of the key shown in Figures 1 to 4 is of circular disk-like form, the sheet metal key stem of the key has a flat head portion the shape of which in plan is substantially that of a circular disk minus approximately a quadrant thereof, and the cap projection I5 and the aperture I"! in the head portion of the stem have the shape of a segment of a circle. The recess i4 and projection l5 of the cap are shaped for tight fitting of the apertured head portion ll of the stem in the recess 14 in holding engagement with the cap skirt to and for tight fitting of the projection IS in the aperture ll. It will be obvious that the perimetrical contours of the key cap, the key stem head portion, theprojection 15 and the aperture ll may be changed; the number of apertures in the stem head and of the projections telescoping therein may be increased; that the body and head portions of the key stem need not be integral with each other; and that the body portion of the key stein may be centrally or otherwise located relatively to the head portion of the stem instead of underlying the head portion adjacent the outer edge of the head portion. The particular shapes of the cap and stem head shown in Figures 1 to 4 are, however, advantageous in affording a good and stable metal support for a molded key cap against finger impacts and in affording strong and positive resistance to relative rotation of the cap and stem.

Figures 5 and 6 show two ways in which the key above described may be modified.

In the construction shown in Figure 5, the sheet metal key stem has a bar-like body part Hi formed integrally with the key lever I3, and has a reduced upper end portion fitted in a central aperture I8 in the sheet metal head part llof the stem and welded or otherwise fixedly held to said head part. Head part ii has the form of a fiat sheet metal disk with a circular periphery and is provided with a plurality of apertures i'i equidistant from its periphery. With such a stem, the plastic key cap would of course have its tubular holding projection or skirt of cylindrical form to snugly fit the periphery of head part II and have a plurality of additional holding projections to snugly fit in the several apertures H.

In the construction shown in Figure 6, the

: sheet metal key stem has a bar-like body part Ill formed integrally with the key lever 13* and has a reduced upper end portion fitted in an off center aperture [8 in the sheet metal head part ll of the stem and welded or otherwise fixedly held to said head part. Head part ll has the form of a flat sheet metal disk with a circular periphery and is provided with a single and centrally located and cruciform aperture 11*. With such a stem, the plastic key cap would of course have its tubular holding projection or skirt of cylindrical form to snugly fit the periphery of head part ll and its additional holding projection of cruciform cross-section to snugly fit in the cruciform aperture M I claim:

1. A typewriter and like key comprising a metal key stem having a plate-like head part at one end thereof formed with an aperture which extends from face to face of said head part, and a plastic key cap removably seated on said platelike head part and having a tubular holding projection which snugly embraces the outer perimetrical edge of said head part substantially entirely around said edge, said key cap also having an additional holding projection which extends longitudinally of said tubular projection and is located within said tubular projection and is snugly embraced by the perimetrical edge of said aperture substantially entirely around said edge.

2. A typewriter and like key, as claimed in claim 1, wherein at least one of said perimetrical edges is non-circular.

3. A typewriter and like key, as claimed in claim 1, wherein the head part of the key stem has a thickness of the order of approximately of an inch, and wherein the length of each of said holding projections of the key cap does not substantially exceed the thickness of said head part of the key stem.

4. A typewriter and like key, as claimed in claim 1, wherein the headpart of the key stem has a circular perimeter and has a plurality of said apertures spaced around the center of said head part equidistant from the perimeter of said head part.

5. A typewriter and like key, as claimed in claim 1, wherein the head part of the key stem has a circular perimeter and the aperture in said head part is non-circular and is centered in said head part.

6. A typewriter and like key comprising a metal key stem having an enlarged head at one end thereof which is provided with an off center aperture, and a plastic key cap removably seated on said head and having a skirt portion telescoped about the outer edge of said head and an off center projection telescoped in said aperture.

7. A typewriter and like key comprising a metal key stem having at one end thereof, and normal thereto and protruding laterally therefrom, a flat key cap supporting and holding head which is provided with an off center aperture, and a molded plastic key cap removably seated on said head and having a skirt portion telescoped about said head and frictionally engaging the outer perimetrical edge of the apertured head and also having an off center projection which is telescoped through said aperture and frictionally engages the aperture-defining inner perimetrical edge of the apertured head.

8. A typewriter or like key, as claimed in claim 7, wherein the stem head directly seats and backs up'the key cap at and adjacent the center of the cap and also directly seats and backs up the key cap adjacent the periphery of said cap around a major part of said cap periphery.

9. A molded plastic key cap, for a key of the kind set forth, characterized by said cap having at its reverse face an off center projection and a skirt portion which are separated by a shallow channel for the insertion into said cap at said reverse face of a flat key stem head having an off center aperture in which said cap projection is engageable, and also to provide two continuous and opposed stem-head-holding friction surfaces on said cap at opposite sides of said channel.

10. A key of the kind having a sheet metal key stem and a key cap of molded plastic which are detachably telescoped end to end in friction holding contact, characterized by said sheet metal key stem having a fiat bar-like main body portion and a flat head portion which is located at one end of said main body portion and normal to said body portion and has opposed faces of much greater area than the transverse cross-sectional area of said body portion, by said head portion of the stem having an oil? center aperture therethrough, and by'said molded plastic key cap being seated on said head portion of the stem and being telescoped in friction holding engagement with said head portion of said stem about both the outer boundary of said head portion and the boundary of the aperture in said head portion to an extent not substantially exceeding the thickness of said head portion.

11. A key, as claimed in claim 10, wherein the body and head portions of the key stem are integral and formed of sheet metal stock having a thickness of approximately /64 of an inch, and the maximum thickness of the molded plastic key cap is approximately /32 of an inch.

12. A key of the kind set forth comprising a key cap supporting flat metal head having the form in plan of three continguous quadrants of a, circular disk and also having therein an off center aperture whose outline is that of a segment of a circle, and a key cap of molded plastic composition removably seated against one face of said head and having a projection extending through said aperture and a skirt portion extending about the perimeter of said head, the peripheral contour of said projection and the internal peripheral contour. of said skirt portion of the cap corresponding in both size and shape respectively with the contours of the head aperture and the head perimeter.

CHARLES H. BRADT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS- Number Name Date 607,193 Quentell July 12, 1898 1,003,361 Kanschine Sept. 12, 1911 1,331,689 Barnaby Feb. 24, 1920 1,364,828 Belknap Jan. 4, 1921 FOREIGN PATENTS Number Country Date 192,167 Switzerland of 1937 

